Generally, a nanofiber refers to a fiber having an average diameter of 5 to 1,000 nm, which may be applicable to the nanofiber prepared or may be prepared according to the present invention. The nanofiber is usually produced by electrospinning a spinning solution, and the nanofiber is electrospun in bottom-up, top-down or parallel production process. Each method has both advantage and disadvantage, but it has been acknowledged that those three known methods are not suitable for the mass-production of nanofiber. In particular, in the case of the top-down electrospinning process, inhomogeneous electrospinning may occur at a certain time or location during the process and it may cause deterioration of the entire quality of the product, which is, therefore, not suitable for mass-production. For this reason, the bottom-up electrospinning process is useful for the mass-production, but a problem sill remain in this process that the electrospinning solution may partially form droplets at an outlet of nozzle due to an inhomogeneous electric field.
Korean Patent Publication No. 2005-0077313 discloses an apparatus for electrospinning nanofiber. The object of the above prior art is to provide an electrospinning apparatus in bottom-up production process, wherein a plurality of nozzles are arranged in narrow space in order to increase the production per unit time and a nozzle block is formed at the lower end of a collector in order to prevent a spinning solution from forming a droplet. In order to achieve the object, the above prior art provides a bottom-up electrospinning devices, wherein the outlets of nozzles installed on a nozzle block are formed in an upper direction and a collector is located on the top part of the nozzle block. Typically, a high voltage of about 20 kV should be applied between the nozzle block and the collector for electrospinning fibers. The apparatus according to the above prior art, however, comprises complicated electric devices relating to the nozzle block and these devices should be insulated from a high voltage of the nozzle block, which makes it difficult to produce nanofiber in large scale.
Another conventional technique is disclosed in Korean Patent No. 10-0679073. The object of the presented prior art is to provide a method for producing nanofiber in a continuous electrospinning process, wherein a collector is inclined at a certain angle against the ground or nozzles are installed forming a certain angle with the collector in order to avoid forming droplets of spinning solution. This process, however, has a disadvantage that a solvent used during the insulating of electric devices and spinning processes may fall down to spinning nozzles.
U.S. Pat. No. 7,134,857 discloses an apparatus for electrospinning nanofiber conducive to mass production using a rotatable spray head and forming an electric field between collectors which is grounded and an electrospining solution is electrospun to the collector guided by the electric field. This process, however, is not suitable for a continuous process.
In order to achieve the mass production of the nanofiber, therefore, an apparatus should be electrically stable and have an improved nozzle block structure capable of homogeneous electrospinning.
The object of the present invention is to provide an electrospinning apparatus for the mass production of nanofibers having electric stability and an improved structure of a nozzle block.